HISTORY / BACKGROUND:
The Colt Model 603 / XM16E1 was the first attempt at providing an improved M-16 for the US Army. The Colt
Model 603 / US Army XM16E1 production ran from early 1964, and transitioned into the Colt Model 603 / US
Army M16A1 in early 1967. It was the first model to incorporate the forward assist feature. This model was
also one of the first to use the "Partial Fence" reinforced lower receiver. This was a "transitional" model and
as such early and late models could have been found with varying component makeups.
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BUTTSTOCK:
STYLE:
Later / Improved Solid Body
Type D
BUTTPLATE:
Solid Rubber
SWIVEL:
Pinned, Metal with
Plastic Covering
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BUFFER GROUP:
BUFFER:
"Original" Edgewater Design
SPRING:
Standard Rifle Spring
TUBE:
Original Tube,
No wrench flats,
Hole in tube at receiver
end to tighten tube
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LOWER RECEIVER:
STYLE:
"Partial Fence"
MARKINGS:
Colt Logo
COLT AR-15
PROPERTY
OF U.S. GOVT.
XM 16 E1
CAL. 5.56 MM.
Serial XXXXXX
SELECTOR:
"Later"
TAKEDOWN / PIVOT PINS:
"Later" Pins
BOLT CATCH/RELEASE:
"Latter" with Raised/Grooved End
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UPPER RECEIVER:
PROOF MARKS / FORGE CODE:
Colt Proof Marks - Triangle & Square with "C"
Located in front of ejection port
No Forge Code
REAR SIGHT:
Raised Directional Markings on Receiver
EJECTION PORT COVER:
"Later" with " Rectangular Plate"
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BOLT GROUP:
CARRIER:
Early - Chrome with
Forward Assist Serrations
Late - Parkerized with
Forward Assist Serrations
BOLT:
Early - Chrome
Late - Parkerized
FIRING PIN:
Improved Light Flat Head
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CHARGING HANDLE:
Current Improved Design
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HANDGUARD SLIP RING:
Flat
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BARREL:
DIAMETER:
0.625" at the Front Sight Base
LENGTH:
20"
TWIST RATE:
1/12
MARKINGS:
Colt Proof Marks
Between FSB Legs
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HANDGUARDS:
Standard Triangular
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FRONT SIGHT BASE:
STYLE:
Early - Cast
Late - Forged, with flash removed
MARKINGS:
Unmarked
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FLASHHIDER:
Early - Improved 3 Prong Flashhider
Late - A1 Birdcage
Unknown Date - Vietnam US Navy SEAL
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Unknown Date - Vietnam US Army LRRP
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RETRO BLACK RIFLE - RIFLE GUIDE - MODEL 603 / XM16E1
Unknown Date - Vietnam US Army
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Unknown Date - Vietnam With Colt 3 x 20 Scope
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ADDITIONAL COLT MODEL 603 / XM16E1 INFORMATION
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.223 Cal / 5.56mm MILITARY RIFLE GUIDE
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